RUI: Novel Heavy Element Transition Metal Oxides; Low Dimensional Magnetism vs. Geometric Magnetic Frustration

RUI：新型重元素过渡金属氧化物；

• 批准号: 1601811
• 负责人: Shahab Derakhshan
• 金额: $ 29.98万
• 依托单位: California State University-Long Beach Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1601811&HistoricalAwards=false
• 关键词: RUI; Novel; Heavy; Element; Transition

NON-TECHNICAL SUMMARY:Magnetic materials have been the subjects of scholarly research for many years. This project will focus on the investigation of a particular class of magnetic systems having triangular arrangements of magnetic ions, which display unusual and little-investigated behavior. The proposed parent materials will also be subjected to chemical modification, and the resulting systems will provide a great opportunity to elucidate the role of crystal symmetry and quantum aspects on determination of the resultant magnetism. A major focus will also be devoted to synthesis of magnetic materials and study of the effects of geometrical and low-dimensional structural contributions. Some of these systems are particularly important as they are expected to exhibit interesting electronic transport properties.The interdisciplinary nature of the project is attractive from an educational perspective for many scientific communities, i.e. chemistry, physics, electronics, materials, etc. Undergraduate and graduate students will be exposed to a large variety of synthetic methods, characterization techniques, and physical properties measurements in the field of solid-state materials chemistry. Some of the research will be conducted in national laboratories, offering valuable opportunities for students to collaborate with other scientists and benefit from hands-on research experience in world-class research facilities. Also, magnetism and magnetic materials are at the basis of many components of daily human life (electric motors, data storage devices, medical imaging technologies, etc.) and this project will advance public awareness of the field of magnetic materials. It will also include development of new courses and programs, attracting students to pursue academic studies in STEM fields, organizing outreach programs in local high schools, and presenting results at scientific conferences. TECHNICAL SUMMARY:In antiferromagnetic (AFM) materials with triangular arrangements of magnetic ions, all the spin constraints cannot be satisfied simultaneously and conventional static magnetic ordering is inhibited. This results in a phenomenon, which is known as geometric magnetic frustration (GMF) where exotic ground states with enormous degeneracies are present. Nonetheless, this condition may be violated when the exchange interactions of different strengths lift the degeneracy and the dominating interaction results in low dimensional magnetism (LDM). This project aims to develop a profound insight into both structural and electronic variables that determine the criteria for the two above-mentioned regimes, LDM vs. GFM. The goals will be achieved by exploratory syntheses, characterizations, and physical properties measurements of rationally designed materials. These will include novel 4d and 5d transition metal oxides in ordered NaCl structure type or in B-site ordered double perovskite structure type, which are composed of triangular magnetic sub-structure. Moreover, the successfully synthesized and characterized parent compounds will undergo further systematic chemical modifications, by which the oxidation states of magnetic ions and/or structural features will be altered. This in turn, will change the degree of frustration and will enable understanding of the interplay between the variables and the ground state magnetic structure. An essential component of the program is the high level of undergraduate and M.S.-level graduate students' participation, particularly those from underrepresented groups, in the societally important area of materials science.

非技术概述：磁性材料多年来一直是学术研究的主题。该项目将重点研究一类特殊的磁性系统，它们具有三角形的磁性离子排列，表现出不寻常的和很少被研究的行为。所提出的母体材料也将进行化学修饰，所得到的系统将提供一个很好的机会来阐明晶体对称性和量子方面在确定合成磁性方面的作用。一个主要的焦点也将致力于磁性材料的合成和研究几何和低维结构贡献的影响。其中一些系统特别重要，因为它们有望表现出有趣的电子输运性质。从教育的角度来看，该项目的跨学科性质对许多科学社区具有吸引力，即化学，物理，电子，材料等。本科生和研究生将接触到固态材料化学领域的各种合成方法、表征技术和物理性质测量。一些研究将在国家实验室进行，为学生提供与其他科学家合作的宝贵机会，并从世界级研究设施的实践研究经验中受益。此外，磁学和磁性材料是人类日常生活中许多部件（电动机、数据存储设备、医疗成像技术等）的基础，该项目将提高公众对磁性材料领域的认识。它还将包括开发新的课程和项目，吸引学生在STEM领域进行学术研究，在当地高中组织外展项目，以及在科学会议上展示成果。技术概述：在具有磁性离子三角形排列的反铁磁材料中，所有自旋约束不能同时得到满足，从而抑制了传统的静态磁有序。这导致了一种被称为几何磁挫折（GMF）的现象，其中存在具有巨大简并的奇异基态。然而，当不同强度的交换相互作用解除简并并导致低维磁性（LDM）时，可能违反这一条件。该项目旨在深入了解决定上述两种制度（LDM和GFM）标准的结构和电子变量。目标将通过探索性的合成、表征和合理设计材料的物理性质测量来实现。这些将包括新的4d和5d过渡金属氧化物，它们是有序NaCl结构型或b位有序双钙钛矿结构型，由三角形磁性亚结构组成。此外，成功合成和表征的母体化合物将进行进一步的系统化学修饰，从而改变磁性离子的氧化态和/或结构特征。反过来，这将改变挫折的程度，并将使理解变量和基态磁结构之间的相互作用。该计划的一个重要组成部分是高水平的本科生和硕士研究生的参与，特别是那些来自代表性不足的群体，在材料科学的社会重要领域。